Information recording medium, recording apparatus, reproduction apparatus, recording method, and reproduction method

ABSTRACT

An information recording medium is provided, which comprises a plurality of recording layers and a first disc information area for storing parameters relating to access to the plurality of recording layers and formats relating to the plurality of recording layers. The first disc information area is provided in a first recording layer which is one of the plurality of recording layers.

This application is a continuation application of U.S. patentapplication Ser. No. 11/753,078 filed on May 24, 2007 now U.S. Pat. No.7,400,571, which is a continuation of U.S. application Ser. No.10/348,027 filed Jan. 20, 2003, now U.S. Pat. No. 7,170,841 issued Jan.30, 2007, the entire disclosures of which are incorporated herein byreference, and is related to sibling U.S. application Ser. Nos.11/154,096 filed Jun. 16, 2005, now U.S. Pat. No. 7,286,455 issued Oct.23, 2007, 11/379,001 filed Apr. 17, 2006, now U.S. Pat. No. 7,212,480issued May 1, 2007, 11/379,013 filed Apr. 17, 2006, now U.S. Pat. No.7,230,907 issued Jun. 12, 2007, 11/456,780 filed on Jul. 11, 2006,11/753,068 filed May 24, 2007, 12/125,429 filed May 22, 2008, 12/125,455also filed May 22, 2008 and U.S. application Ser. No. 12/131,554, filedon Jun. 2, 2008.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an information recording mediumcomprising at least two recording layers, a method and apparatus forrecording information onto this medium, and a method and apparatus forreproducing information from this medium.

2. Description of the Related Art

In recent years, various information recording media capable ofrecording/reproducing a large volume of information have been developed.Among them are optical discs. One of large-capacity optical discs is adouble-sided optical disc comprising two optical discs attachedtogether, on each of which information can be recorded/reproduced.However, there is a demand for a high-capacity, but single-sided andrandom access disc which is unnecessary to be turned upside down, forsome applications, such as computers, games, and the like, in whichrandom accesses are frequently required.

To meet such a demand (high-capacity, random access, and single-sided),it is conceivable that a single optical disc comprises at least tworecording layers (such an optical disc may be referred to be amulti-layer optical disc), where information can be recorded/reproducedon a single side thereof. FIG. 7 shows a configuration of an opticaldisc 700 comprising two recording layers on one side thereof.

The optical disc 700 comprises a first recording layer 704, a firstsubstrate 705, an adhesive resin 703, a second substrate 701, and asecond recording layer 702. Each substrate is provided with a clamp hole706. The second recording layer 702 comprises a disc information area707 and a data area 710. The first recording layer 704 comprises a discinformation area 711 and a data area 714.

The first substrate 705 and the second substrate 701 are made ofpolycarbonate resin or the like and are used to protect the firstrecording layer 704 and the second recording layer 702, respectively.The disc information area 707 is a reproduction-only area in whichinformation, such as the power of laser light to irradiate the secondrecording layer 702 and the like. The disc information area 711 is alsoa reproduction-only area in which information, such as the power oflaser light to irradiate the first recording layer 704, and the like.

In the optical disc 700, for example, reproduction is first performed onthe first recording layer 704, immediately followed by reproduction onthe second recording layer 702. In this case, reproduction operationsare performed in the following order: information indicating the powerof laser light for irradiating the first recording layer 704 isreproduced from the disc information area 711; reproduction is performedon the data area 714; information indicating the power of laser lightfor irradiating the second recording layer 702 is reproduced from thedisc information area 707; and reproduction is performed on the dataarea 710. Alternatively, reproduction operations are performed on thedisc information area 711, the disc information area 707, the data area714, and the data area 710 in this order. Thus, in the optical disc 700,information has to be reproduced from two disc information areas.Therefore, it takes a long time to reproduce information of theparameters and formats of the optical disc 700, such as the power oflaser light and the like.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, an informationrecording medium comprises a plurality of recording layers, and a firstdisc information area for storing parameters relating to access to theplurality of recording layers and formats relating to the plurality ofrecording layer. The first disc information area is provided in a firstrecording layer which is one of the plurality of recording layers.

In one embodiment of this invention, an address is assigned to the firstrecording layer. The parameters include first irradiation powerinformation indicating a value of a power of laser light which is usedto irradiate the first recording layer, and second irradiation powerinformation indicating a value of power of laser light which is used toirradiate another recording layer of the plurality of recording layers.An address assigned to an area in the first disc information area inwhich the first irradiation power information is stored is smaller thanan address assigned to an area in the first disc information area inwhich the second irradiation power information is stored.

In one embodiment of this invention, the information recording mediumfurther comprises a second disc information area for storing the sameinformation as that of the first disc information area. The second discinformation area is provided in a second recording layer which isanother one of the plurality of recording layers.

In one embodiment of this invention, the first recording layer is one ofthe plurality of recording layers which is previously determined as areference layer.

In one embodiment of this invention, the plurality of recording layersare recording layers capable of recording information. The informationrecording medium further comprises a plurality of adjustment areas foradjusting recording power of laser light. Each of the plurality ofrecording layers comprises a corresponding one of the plurality ofadjustment areas.

In one embodiment of this invention, the second recording layer which isone of the plurality of recording layers comprises a buffer area. Thebuffer area is contiguous to one of the plurality of adjustment areasincluded in the second recording layer.

In one embodiment of this invention, each of the plurality of adjustmentareas is provided at a different radial position on the informationrecording medium.

In one embodiment of this invention, the information recording medium isa write-once-read-many information recording medium.

In one embodiment of this invention, an address is assigned to the firstrecording layer. The parameter includes a first parameter relating toaccess to the first recording layer and a second parameter relating toanother one of the plurality of recording layers. An address assigned toan area in the first disc information area in which the first parameteris stored is smaller than an address assigned to an area in the firstdisc information area in which the second parameter is stored.

In one embodiment of this invention, an address is assigned to the firstrecording layer. The format includes a first format relating to thefirst recording layer and a second format relating to another one of theplurality of recording layers. An address assigned to an area in thefirst disc information area in which the first format is stored issmaller than an address assigned to an area in the first discinformation area in which the second format is stored.

In one embodiment of this invention, the information recording mediumfurther comprises a data area for recording user data provided in theplurality of recording layers. The plurality of recording layers areprovided with a groove. A second recording layer which is one of theplurality of recording layers, comprises an area at the same radialposition as that of the first disc information area and an area in whicha portion of the data area is provided. A type of a shape of the grooveprovided in the area at the same radial position of the first discinformation area is the same as a type of a shape of the groove providedin the area in which the portion of the data area is provided.

In one embodiment of this invention, a groove is provided in at least aportion of the plurality of recording layers. A second recording layerwhich is one of the plurality of recording layers does not have a groovein an area which is a portion of the second recording layer at the sameradial position as that of the first disc information area.

In one embodiment of this invention, the plurality of recording layersare provided with a groove. A type of a shape of the groove in a secondrecording layer which is one of the plurality of recording layers isconstant.

In one embodiment of this invention, the first recording layer isprovided with a groove. A type of a shape of the groove in the firstdisc information area is different from a type of a shape of the groovein an area which is a portion of the first recording layer and iscontiguous to the first disc information area.

In one embodiment of this invention, the first recording layer isprovided with a groove. The groove in the first disc information area iscontinuous to the groove in an area which is a portion of the firstrecording layer and is contiguous to the first disc information area.

In one embodiment of this invention, the parameter and the formatinclude a first parameter and a first format relating to the firstrecording layer. The parameter and the format include a second parameterand a second format relating to a second recording layer which isanother one of the plurality of recording layers. The length of an areaof the first disc information area storing the first parameter and thefirst format is the same as the length of an area of the first discinformation area storing the second parameter and the second format.

In one embodiment of this invention, the parameter includes a firstparameter relating to access to the first recording layer. The formatincludes a first format relating to the first recording layer. A set ofthe first parameter and the first format are continuously repeated andstored in the first disc information area.

In one embodiment of this invention, the parameter includes a secondparameter relating to access to a second recording layer which isanother one of the plurality of recording layers. The format includes asecond format relating to the second recording layer. A set of thesecond parameter and the second format are continuously repeated andstored in the first disc information area.

In one embodiment of this invention, the disc information area stores aplurality of sets of the parameter and the format.

In one embodiment of this invention, the information recording mediumfurther comprises a dummy area. The plurality of sets includes a firstset and a second set. The dummy area is provided between a first areaprovided with the first set, the first area being a portion of the firstdisc information area, and a second area provided with the second set,the second area being another portion of the first disc informationarea.

In one embodiment of this invention, the length of the dummy area is anintegral multiple of the length of an area storing a set of theparameter and the format.

In one embodiment of this invention, an address is assigned to the firstrecording layer. The parameter includes a first parameter relating toaccess to the first recording layer and a second parameter relating toanother one of the plurality of recording layers. The first parameterand the second parameter are stored in an area having the same addressassigned thereto in the first disc information area.

In one embodiment of this invention, an address is assigned to the firstrecording layer. The format includes a first format relating to accessto the first recording layer and a second format relating to another oneof the plurality of recording layers. The first format and the secondformat are stored in an area having the same address assigned thereto inthe first disc information area.

According to another aspect of the present invention, a recordingapparatus for recording information into an information recording mediumis provided. The information recording medium comprises a plurality ofrecording layers, and a disc information area for storing parametersrelating to access to the plurality of recording layers and formatsrelating to the plurality of recording layer. The disc information areais provided in a first recording layer which is one of the plurality ofrecording layers. The recording apparatus comprises an optical headcapable of optically writing the information into the informationrecording medium, and a control section for controlling recording usingthe optical head. The recording comprises the steps of reproducing theparameter and the format stored in the disc information area, andrecording the information into the information recording medium based onthe reproduced parameter and format.

According to another aspect of the present invention, a reproductionapparatus for reproducing information from an information recordingmedium is provided. The information recording medium comprises aplurality of recording layers, and a disc information area for storingparameters relating to access to the plurality of recording layers andformats relating to the plurality of recording layer. The discinformation area is provided in a first recording layer which is one ofthe plurality of recording layers. The reproduction apparatus comprisesan optical head capable of optically reading the information from theinformation recording medium, and a control section for controllingreproduction using the optical head. The reproduction comprises thesteps of reproducing the parameter and the format stored in the discinformation area, and reproducing the information from the informationrecording medium based on the reproduced parameter and format.

According to another aspect of the present invention, a recording methodfor recording information into an information recording medium isprovided. The information recording medium comprises a plurality ofrecording layers; and a disc information area for storing parametersrelating to access to the plurality of recording layers and formatsrelating to the plurality of recording layer. The disc information areais provided in a first recording layer which is one of the plurality ofrecording layers. The recording method comprises the steps ofreproducing the parameter and the format stored in the disc informationarea, and recording the information into the information recordingmedium based on the reproduced parameter and format.

According to another aspect of the present invention, a reproductionmethod for reproducing information from an information recording mediumis provided. The information recording medium comprises a plurality ofrecording layers, and a disc information area for storing parametersrelating to access to the plurality of recording layers and formatsrelating to the plurality of recording layer. The disc information areais provided in a first recording layer which is one of the plurality ofrecording layers. The reproduction method comprises the steps ofreproducing the parameter and the format stored in the disc informationarea, and reproducing the information from the information recordingmedium based on the reproduced parameter and format.

Thus, the invention described herein makes possible the advantages ofproviding an information recording medium comprising at least tworecording layers, a method and apparatus for recording information ontothis medium, and a method and apparatus for reproducing information fromthis medium, in which the time required to reproduce information fromthe disc information area is reduced.

These and other advantages of the present invention will become apparentto those skilled in the art upon reading and understanding the followingdetailed description with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing an optical disc according to an embodimentof the present invention.

FIG. 2A is a diagram showing a track provided in a recording layeraccording to an embodiment of the present invention.

FIG. 2B is a diagram showing a track provided in a recording layeraccording to an embodiment of the present invention.

FIG. 2C is a diagram showing a track provided in a recording layeraccording to an embodiment of the present invention.

FIG. 2D is a diagram showing a track provided in a recording layeraccording to an embodiment of the present invention.

FIG. 3 is a diagram showing a recording/reproduction apparatus accordingto an embodiment of the present invention.

FIG. 4A is a diagram showing a track according to an embodiment of thepresent invention.

FIG. 4B is a diagram showing a track according to an embodiment of thepresent invention.

FIG. 4C is a diagram showing a recording/reproduction apparatusaccording to an embodiment of the present invention.

FIG. 4D is a diagram showing assignment of an address number to arecording layer according to an embodiment of the present invention.

FIG. 5A is a diagram showing a track according to an embodiment of thepresent invention.

FIG. 5B is a diagram showing a track according to an embodiment of thepresent invention.

FIG. 5C is a diagram showing a recording/reproduction directionaccording to an embodiment of the present invention.

FIG. 5D is a diagram showing assignment of an address number to arecording layer according to an embodiment of the present invention.

FIG. 6A is a layout of information in a disc information area.

FIG. 6B is a layout of information in a disc information area.

FIG. 7 is a diagram showing a conventional optical disc.

FIG. 8A is a diagram showing an optical disc according to an embodimentof the present invention.

FIG. 8B is a diagram showing an optical disc according to an embodimentof the present invention.

FIG. 9 is a diagram showing an optical disc according to an embodimentof the present invention.

FIG. 10 is a diagram showing an optical disc according to an embodimentof the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention will be described by way ofillustrative examples with reference to the accompanying drawings.

FIG. 1 shows a rewritable optical disc 100 comprising two recordinglayers according to an embodiment of the present invention.

The optical disc 100 comprises a first recording layer 104, a firstsubstrate 105, an adhesive resin 103, a second substrate 101, and asecond recording layer 102. Each of these substrates and recordinglayers is provided with a clamp hole 106. The optical disc 100 has adata area 115 for recording user data. The data area 115 is provided onboth the first recording layer 104 and the second recording layer 102.The data area 115 comprises a data area 110 provided on the secondrecording layer 102 and a data area 114 provided on the first recordinglayer 104.

The second recording layer 102 comprises a disc information area 107, adefect list area 108, a spare area 109, and the data area 110. The firstrecording layer 104 comprises a disc information area 111, a defect listarea 112, a spare area 113, and the data area 114. The first recordinglayer 104 and the second recording layer 102 are provided on one side ofthe optical disc 100.

The disc information area 107, the defect list area 108, the spare area109, the data area 110, the disc information area 111, a defect listarea 112, the spare area 113, and the data area 114 are each providedwith a plurality of spiral or concentric tracks. Each track comprises aplurality of sectors.

Here, the defect list area 108, the spare area 109, the data area 110,the defect list area 112, the spare area 113, and the data area 114 arerecordable areas, in which the track is meandering at predeterminedcycles. Referring to FIG. 2B, address information or the like can berecorded in a track by overlaying a high frequency component onto atrack. Alternatively, referring to FIG. 2C, address information or thelike can be recorded in a track by replacing a segment corresponding toan integral multiple of a predetermined cycle with a segment having adifferent frequency. Alternatively, referring to FIG. 2D, the segmentcorresponding to an integral multiple of a predetermined cycle may bereplaced with a segment having a partially modulated pattern or acombination of frequencies. By forming the type of the shape of thetrack as shown in FIG. 2C and FIG. 2D, the continuity of the phase of apredetermined cyclic portion can be obtained, thereby making it easy toperform clock extraction.

The first substrate 105 and the second substrate 101 are made of apolycarbonate resin or the like and are used to protect the firstrecording layer 104 and the second recording layer 102, respectively.The disc information area 107 is a reproduction-only area in whichparameters for accessing the first recording layer 104 and the secondrecording layer 102 and the formats of the first recording layer 104 andthe second recording layer 102. The disc information area 111 is also areproduction-only area in which the parameters for accessing the firstrecording layer 104 and the second recording layer 102 and the formatsof the first recording layer 104 and the second recording layer 102. Thedisc information area 111 records the same information as that in thedisc information area 107. The optical disc 100 may have both the discinformation area 107 and the disc information area 111, or either thedisc information area 107 or the disc information area 111. Theparameters stored in the disc information area 107 are secondirradiation power information indicating the irradiation power of laserlight appropriate for the second recording layer 102 when information isrecorded/reproduced on the second recording layer 102 and firstirradiation power information indicating the irradiation power of laserlight appropriate for the first recording layer 104 when information isrecorded/reproduced on the first recording layer 104. The parametersstored in the disc information area 111 are second irradiation powerinformation indicating the irradiation power of laser light appropriatefor the second recording layer 102 when information isrecorded/reproduced on the second recording layer 102 and firstirradiation power information indicating the irradiation power of laserlight appropriate for the first recording layer 104 when information isrecorded/reproduced on the first recording layer 104. Information isrecorded on the medium by modulating a track radially for each cycle orevery double cycle. An example of the track modulation is shown in FIG.2A.

In this embodiment, different types of track shapes are used betweenreproduction-only areas (e.g., the disc information area 107, the discinformation area 111, and the like) and recordable areas (e.g., thedefect list area 108, the spare area 109, the data area 110, the defectlist area 112, the spare area 113, the data area 114, and the like).Thereby, an optical disc recording/reproduction apparatus can determinewhether or not an area on which reproduction is currently performed is adisc information area, before reproducing an address recorded in atrack.

For multi-layer discs, the irradiation power of laser light, which isused to reproduce information from the farthest layer from the discsurface through which the information is read, may be greater than theirradiation power of laser light, which is used for single-layer discs.Therefore, the irradiation power of laser light for single-layer discsmay be insufficient to reproduce an address from the optical disc 100,however, may be sufficient to recognize a disc information area based onthe waveform of a tracking signal derived from the shape of a trackgroove.

FIG. 3 shows a recording/reproduction apparatus 300 according to anembodiment of the present invention. The recording/reproductionapparatus 300 comprises a spindle motor 302, an optical head 303, alaser light control circuit 304, a servo circuit 305, a reproductionbinarization circuit 306, a digital signal processing circuit 307, arecording compensation circuit 308, and a CPU 309.

The optical disc 100 (FIG. 1) is loaded into the recording/reproductionapparatus 300. The recording/reproduction apparatus 300 transmits andreceives information to and from a host PC 310.

The CPU 309, which functions as a control section, controls alloperations within the recording/reproduction apparatus 300 in accordancewith a built-in control program. As described below, the optical head303 optically writes information the optical disc 100 on the one sidethereof. Further, the optical head 303 can optically read informationfrom the optical disc 100. The CPU 309 controls recording andreproduction operations using the optical head 303. The recordingoperation comprises the steps of reproducing parameters and formatsstored in a disc information area, and recording user data onto theoptical disc 100 based on the reproduced parameters and formats. Thereproduction operation comprises the steps of reproducing parameters andformats stored in a disc information area, and reproducing user datarecorded in the optical disc 100 based on the reproduced parameters andformats. Hereinafter, an operation of the recording/reproductionapparatus 300 will be described in detail.

The optical disc 100 has the structure as described above with referenceto FIG. 1. The spindle motor 302 is a motor for rotating the opticaldisc 100. The optical head 303 irradiates the optical disc 100 withlaser light as well as converts laser light 311 reflected from theoptical disc 100 into an electric signal to output a reproductionsignal. The laser light control circuit 304 controls the power of laserlight output from the optical head 303. These controls are carried outin accordance with instructions from the CPU 309. The servo circuit 305controls the position of the optical head 303, focusing, tracking, andthe rotation of the spindle motor 302. The reproduction binarizationcircuit 306 subjects the reproduction signal (data information is anaddition signal, and information relating to a disc information area oran address is a subtraction signal) obtained by the optical head 303 toamplification and binarization to produce a binarization. A built-in PLL(not shown) is used to produce clocks synchronized with the binarizationsignal.

The digital signal processing circuit 307 subjects the binarizationsignal to a predetermined demodulation process or error correctionprocess. When recording data, the recorded data is subjected to an errorcorrection code addition process and a predetermined demodulationprocess to produce the modulated data. The recording compensationcircuit 308 converts the modulated data into optically modulated datacomprising a pulse sequence, and also delicately adjusts the pulse widthor the like of the optically modulated data based on the reproductionsignal of a disc information area or data previously stored in the CPU309 so as to produce a recording pulse signal suitable for pitformation. The CPU 309 controls all operations within therecording/reproduction apparatus 300. The host PC 310 comprises acomputer (not shown), an application (not shown), an operating system(not shown), and the like, and requests the recording/reproductionapparatus 300 to perform recording or reproduction of information.

When the optical disc 100 is loaded into the recording/reproductionapparatus 300, information is reproduced from the disc information area111 using the optical head 303 having a predetermined irradiation powerin accordance with signals from the laser light control circuit 304 andthe servo circuit 305. In this case, the reproduced information isirradiation power information which is used to record information (userdata) into the first recording layer and the second recording layer, orthe like. When requested by the host PC 310, the CPU 309 sets arecording power for recording information into the first recording layer104 to the laser light control circuit 304, and controls the opticalhead 303 to record information into the data area 114. Next, the CPU 309sets a recording power for recording information into the secondrecording layer 102 to the laser light control circuit 304, and controlsthe optical head 303 to record information into the data area 110.

The disc information area 111 of the optical disc 100 contains theparameters and formats (irradiation power information for recording, orthe like) of both the first recording layer 104 and the second recordinglayer 102, whereby information is reproduced from the disc informationarea only once. Therefore, the time required to access to a discinformation area can be reduced as compared to when information isreproduced from the disc information area 107 to record data into thesecond recording layer 102 while information is reproduced from the discinformation area 111 to record data into the first recording layer 104.

In this embodiment, parameter and formats are recorded in both the discinformation area 107 and the disc information area 111, thereby makingit possible to obtain irradiation power information or the like fromeither layer. Therefore, even when information is reproduced from alayer different from a predetermined recording layer due to theirregular thickness of the adhesive resin 103 or disturbances in thefocusing control of the servo circuit 305, information required forrecording can be reproduced and obtained from that layer.

In this embodiment, irradiation power information and the like arerecorded in both the disc information area 107 and the disc informationarea 111. Therefore, the time required before recording data can bereduced, for example, by reproducing information from the discinformation area 111 when recording data into the data area 114 first orreproducing information from the disc information area 107 whenrecording data into the data area 110 first.

In this embodiment, the optical disc 100 has two layers, i.e., the firstrecording layer 104 and the second recording layer 102. Alternatively,the optical disc 100 may have three or more recordable recording layers.In this embodiment, the recording formats of information recorded in thedisc information area 107 and the disc information area 111 are suchthat the meandering pattern of a track is radially modulated for eachfundamental cycle and every double cycle. Alternatively, as shown inFIG. 2B, information may be recorded in a track meandering atpredetermined cycles by overlaying a high frequency component onto thetrack. Alternatively, as shown in FIGS. 2C and 2D, information can berecorded in a track meandering at predetermined cycles by replacing asegment of the track with a segment having a different frequency orpattern. Particularly, by using the same type of the shape of the trackgroove, it is possible to produce a substrate more easily.

In this embodiment, the disc information area 107 and the discinformation area 111 each have a plurality of spiral or concentrictracks. Information may be recorded in the disc information area 107 andthe disc information area 111 in the form of pits and lands. Informationmay be recorded in a disc information area by the same method as thatfor recording data into a data area before factory shipment or the like.

The disc information area 107 and the disc information area 111 may havea track pitch (or a pit pitch in a radial direction) different fromthose of the defect list area 108, the spare area 109, the data area110, the defect list area 112, the spare area 113, and the data area 114(or a pit pitch in a radial direction). By expanding the track pitch ina disc information area, the influence of contiguous tracks can bereduced.

By expanding the track pitch or the pit pitch in a disc information areato be greater than the track pitch or the pit pitch of a recordablearea, such as a data area or the like, it is possible to reproduceinformation from a disc information area even when using an optical discapparatus having an optical head with along laser wavelength, forexample. In this case, a minimum of information can be returned to theuser. In other words, by expanding the compatibility of a discinformation area between different types of optical disc apparatuses,even when information cannot be recorded due to the apparatusspecification, the reason that recording cannot be performed can beclarified.

When the spot of laser light is vertically shifted from one layer toanother layer, it is difficult to locate the spot at the same radialposition due to misalignment of substrates attached together,misalignment of the clamp holes of the substrates, or the like. Forexample, when it is attempted to move from the 1000^(th) track from theinside circumference of the first recording layer 104 to the 1000^(th)track from the inside circumference of the second recording layer 102,an error of about ±50 tracks occurs. Therefore, when the spot of laserlight is shifted from layer to layer in the vicinity of a boundarybetween a reproduction-only track and a recordable track, if the trackon the destination layer is discontinuous, a reproduction or recordingoperation becomes unstable and cannot be quickly performed.

Therefore, even when the track pitch of the disc information area 107and the disc information area 111 is different from the track pitch ofthe defect list area 108, the spare area 109, the data area 110, thedefect list area 112, the spare area 113, and the data area 114, it isdesirable that the track groove of the disc information area 107 iscontinuously linked to the track groove of an area contiguous to thedisc information area 107 (e.g., the area is the defect list area 108 inthe example of FIG. 1; and the area may be the spare area 109 or thedata area 110). Similarly, it is desirable that the track groove of thedisc information area 111 is continuously linked to the track groove ofan area contiguous to the disc information area 111 (e.g., the area isthe defect list area 112 in the example of FIG. 1; and the area may bethe spare area 113 or the data area 114). It is desirable thattransition of the track pitch is completed within about 100 tracks inview of data capacity. However, it is desirable that pitches are variedas moderately as possible. In view of servo, the difference between thetrack pitch of a disc information area and the track pitch of a defectlist area, a spare area, or a data area is desirably about 10% and about15% at maximum in order to perform reproduction quickly when the spot oflaser light is shifted to a track on any layer.

In this embodiment, as shown in FIG. 2A, disc information is recorded ina disc information area by modulating a track radially for eachfundamental cycle and every double cycle. As shown in FIG. 2B, FIG. 2C,and FIG. 2D, address information or the like is recorded in a defectlist area, a spare area, and a data area by partiallyfrequency-modulating a track meandering at predetermined cycles, oroverlaying a high frequency component on the track. In the whole or apart of the transition area of track pitches, tracks may be formed in amodulation manner which is not used in any of a disc information area, adefect list area, a spare area, and a data area, or may not bemodulated, or may not be meandering.

Thus, by changing the modulation method or the type of shape between thetransition area of track pitches and its contiguous areas before andafter the transition area, the recording/reproduction apparatus 300 canrecognize the transition area quickly.

As described above, discontinuity is removed from a boundary betweenareas having different track pitches. Therefore, it is possible toquickly start processing in a destination area in an optical disc havinga discontinuous portion as compared to when the spot of laser light ismoved from a start position to the destination area which is largelyradially distant from the discontinuous portion (starting position).

In this embodiment, a disc information area is provided in the mostinside circumference of a disc. Alternatively, a disc information areamay be provided in the most outside circumference of a disc, or both theinside and outside circumferences of a disc.

In this embodiment, the disc information area 107 and the discinformation area 111 each contain irradiation power information and thelike for both the first recording layer and the second recording layer.If a layer(s) on which reproduction is performed is specified, not alllayers may contain irradiation power information and the like for alllayers in their disc information areas.

A recording layer of the optical disc 100, which is located atsubstantially the same distance from the disc surface of the opticaldisc 100, through which information is read, as the distance from thedisc surface of an optical disc comprising a single recording layer,through which information is read, is used as a reference layer. Atleast the reference layer may contain a disc information area.Therefore, disc information for any layer of the optical disc 100 can beobtained using a recording/reproduction apparatus for perform recordingand reproduction on an optical disc comprising a single recording layer,thereby making it possible to simplify the structure of therecording/reproduction apparatus. A recording layer as a reference layer(e.g., the first recording layer 104) is previously determined from aplurality of recording layers.

Note that a degradation in a reproduction signal due to tilt isincreased with an increase in distance from the disc surface. Therefore,it is desirable that the reference layer is located at substantially thesame distance from the disc surface as the distance of the layer of asingle-layer disc from the disc surface and the reference layer is thefarthest layer from the disc surface. In this case, when the type of theshape of an area, which is a portion of a recording layer other than thereference layer and is located at the same radial position as that of adisc information area of the reference layer, is the same as the type ofthe shape of a data area in which user data is recorded, transmittancescan be the same irrespective of the radial position. Therefore, noparticular detection means for reproducing information from a discinformation area of a reference layer is required, whereby theconfiguration of a recording/reproduction apparatus can be simplifiedand it is easier to produce a recording layer.

Particularly, in a multi-layer disc comprising a plurality of recordinglayers, the type of the shape of grooves in a recording layer(s) otherthan a reference layer is the same as the type of the shape of groovesin a data area (only one type of the shape of grooves is used), therebysimplifying production of a substrate.

When a reference layer contains a disc information area, it is possibleto reduce the scatter of light in a recording layer(s) other than thereference layer by providing an area, which is a portion of a recordinglayer other than the reference layer and is located at the same radialposition as that of a disc information area of the reference layer, withno groove (i.e., flat structure). Therefore, the quality of areproduction signal from the reference layer can be improved.

By providing a disc information area only in a reference layer, it iseasy to determine whether or not a currently reproduced recording layeris the reference layer by reproducing an area around a radial positionat which a disc information area of an optical disc is provided.

A disc information area may store parameters relating to a plurality ofrecording layers, such as recommended irradiation power information forreproduction, recommended irradiation power information for recording,maximum irradiation power information, a pulse width in recording, aratio between a plurality of irradiation powers combined in recording, amargin constant used in determining an irradiation power optimal forrecording, and the like.

A disc information area may contain formats relating to a plurality ofrecording layers, such as the name of a disc, the size of a disc,version information, the disc type of any layer (i.e., an identifierindicating whether a layer is a recordable/reproducible layer or areproduction-only layer), the number of all recordable layers, thenumber of all reproduction-only layers, and the number of all layers.The disc information area further contains formats relating to aplurality of recording layers, such as an identifier indicating whetheror not information in any layer can be copied, clock information, anidentifier for indicating whether or not BCA (Burst Cutting Area) forproviding specific information after production of a disc is provided, atransfer rate, recording/reproduction directions, a physical addressstart number, a physical address end number, a logical address startnumber, a logical address end number, a shortest mark length, arecording rate, and the like.

By setting parameters required for recording and reproduction in eachrecording layer, the degree of freedom in designing discs can beimproved. For example, when a plurality of recording layers are used toachieve high-density recording, variations in reflection in at leastlayers through which light is transmitted have to be taken intoconsideration. Therefore, a higher level of precision design is requiredthan when recording is performed on only one recording layer. In thiscase, for example, if the first recording layer 104 and the secondrecording layer 102 have to be reproduced with the same irradiationpower, it is inferred that the optical disc 100 has difficulty indesigning recording layers. For example, the recording performance ofthe second recording layer 102 has to be secured under a hightransmittance situation. To avoid this, irradiation power forreproduction is not limited, and instead, irradiation power informationis recorded in a disc information area. Therefore, irradiation power canbe increased when reproduction is performed in the first recording layer104. The degree of freedom in designing a recording film of the secondrecording layer 102 can be increased.

By recording parameters required for recording and reproduction to beperformed on any layer together into a disc information area of at leastone recording layer, it is possible to quickly grasp a control methodoptimal to the whole disc.

BCA is used to further classify discs having the same contents in theirdisc information areas. Classification is recorded in the form of a barcode after production of discs. BCA is provided in at least one layer,and desirably in a reference layer. In this case, by providing a layercontaining no BCA with a groove shape different from that of thereference layer, it is easy to recognize the reference layer byperforming reproduction within a radial range of the reference layer inwhich BCA is provided. Particularly, in a recording layer other than thereference layer, a radial range in which BCA is provided is providedwith a flat structure having no groove, thereby making it possible toreduce the scatter of light in other layers. Moreover, the quality of areproduction signal from BCA can be improved and production of asubstrate is facilitated.

Recording of information into BCA requires irradiation with laser havinga power much higher than a power required when performing recording on arecordable area. Therefore, it is likely that the characteristics of therecording film of a recordable area, such as a defect list area, a sparearea, a data area, or the like, is damaged. Therefore, it is desirablethat recordable areas contain no BCA as well as no variation inrecording positions. If a recordable area is contiguous to an area inwhich BCA is provided, it is desirable to provide a buffer area in whichno intended use is defined between these areas. In this case, the netvolume of the recordable area is reduced.

According to the above-described viewpoint, it is typically desirable toprovide an area, in which BCA is provided, at an end in a radialdirection. It is not preferable to provide BCA at the outsidecircumference, since information in BCA is required when actuating aswell as from the viewpoint of capacity. As shown in FIG. 8A, it isdesirable to provide BCA in a more inside circumference than a discinformation area. As described above, a disc is irradiated with a highpower of laser when recording information into BCA, it is likely todamage data already recorded in a reproduction-only area. Therefore, asshown in FIG. 8B, a buffer portion, in which dummy data, such as, forexample, “0”, is provided, may be provided at an inside circumference ofa disc information area (a disc information area 801A), and in fact,data is recorded at an outside circumference thereof (a disc informationarea 801B).

In this embodiment, disc information is recorded in a disc informationarea by radially modulating tracks for each fundamental cycle and everydouble cycle. Alternatively, a modulation method different from that fora disc information area may be used in an area in which BCA is provided.Conversely, tracks may be straight grooves with no modulation or may bemeandering at predetermined cycles. Further, a track pitch may bedifferent between an area provided with BCA and a disc information area.In this case, since it is likely that a track groove is damaged due torecording of information into BCA, the area containing BCA desirably hasa larger track pitch.

As described above, it is possible for a recording/reproductionapparatus to quickly distinguish an area provided with BCA from a discinformation area by changing a track modulation method and the type ofthe shape of a track.

In general, when the spot of laser light is vertically shifted from onelayer to another layer, it is difficult to locate the spot at the sameradial position due to misalignment of substrates attached together,misalignment of the clamp holes of the substrates, or the like. Forexample, when it is attempted to move from the 1000^(th) track from theinside circumference of the first recording layer 104 to the 1000^(th)track from the inside circumference of the second recording layer 102,an error of about ±50 tracks occurs. Therefore, when the spot of laserlight is shifted from layer to layer in the vicinity of a boundarybetween a reproduction-only track and a recordable track, if the trackon the destination layer is discontinuous, a reproduction operationbecomes unstable and cannot be quickly performed. Therefore, even whenan area in which BCA is provided and a disc information area havedifferent track pitches, it is desirable that these areas arecontinuously linked together. Moreover, it is desirable that trackpitches are moderately changed.

It is desirable that irradiation power information for reproductionprecedes irradiation power information for recording. In this case, whena request from a host PC is reproduction, data can be quickly reproducedif the irradiation power information for recording is not reproduced.

Parameters and formats recorded in a disc information area required forperforming recording and reproduction on any layer may be recorded intracks in the defect list area 108, the spare area 109, the data area110, the defect list area 112, the spare area 113, and the data area114. Since such information is recorded in any track, for example, whena request for reproduction is received from the host PC 310, informationminimally required for reproduction, such as irradiation power or thelike, is reproduced from the disc information area which does not have arisk of deleting user data with irradiation power for reproduction.Next, the remaining information, such as, for example, irradiation powerinformation for recording which is expected to be used when a requestfor recording is next received, or the like, is reproduced from tracksin a data area for a rotation waiting time, thereby making it possibleto quickly reproduce data.

Parameters and formats may be recorded by the same method as used forrecording of address information into each area or by a method differentfrom a method for recording address information.

Parameters and formats recorded in a disc information area may berecorded in not all of the defect list area 108, the spare area 109, thedata area 110, the defect list area 112, the spare area 113, the dataarea 114, and the like. For example, when parameters and formats are notrecorded in the data area 114, a recording/reproduction apparatus canrecognize the data area 114 as a data area even if the data area 114 hasthe same track shape as that of other areas since no parameter or formatis present therein.

Parameters and formats for all layers may not be recorded in tracks ofthe defect list area 108, the spare area 109, the data area 110, thedefect list area 112, the spare area 113, and the data area 114. Eachlayer may contain only its own parameters and formats. Each layer mayfurther contain minimally required information for other layers inaddition to its own parameters and formats. Since information for otherlayers is not recorded, a more number of copies of address informationcan be recorded, for example. A disc substrate can be easily produced byincorporating information for other layers to be combined into the mostinside portion.

Next, address numbers will be described with reference to FIGS. 4A to 4Dand FIG. 5A to 5D. FIGS. 4A to 4D show an example of tracks,recording/reproduction directions, and address numbers. FIG. 4A shows apattern of spiral grooves in the first recording layer 104. FIG. 4Bshows a pattern of spiral grooves in the second recording layer 102.FIG. 4C shows the recording/reproduction directions of the optical disc100. FIG. 4D shows assignment of address numbers. When the optical disc100 is rotated, the optical head 303 is moved from the insidecircumference to the outside circumference along a track 401 or 402.When data is sequentially recorded, for example, recording is performedfrom the most inside circumference to the most outside circumference ofthe data area 114, and then from the most inside circumference to themost outside circumference of the data area 110. Physical addressnumbers 403 and logical address numbers 404 in each recording layer areincremented in the recording/reproduction directions. The physicaladdress number 403 may not be started from 0 and may not be continuousat a boundary between the first and second layers.

For example, layer numbers may be contained in the physical addressnumber 403, and may be located at an upper portion of the physicaladdress number 403. The logical address numbers 404, which arecontinuously incremented from 0, are assigned to all data areas on adisc. In the data area 114 of the first layer, the logical addressnumber 404 is 0 at the most inside circumference and is incremented oneby one toward the outside circumference. In the data area 110 of thesecond layer, the logical address number 404 is incremented one by onefrom the most inside circumference toward the outside circumference,starting from the greatest number of the first layer plus 1. Referencenumerals 405 and 406 indicate lead-out areas (not shown in FIG. 1),which are provided in order to allow the optical head 303 to follow atrack even when the optical head 303 overrun a data area.

As shown in FIGS. 4A to 4D, it is easier to produce substrates havingthe same spiral direction than substrates having different spiraldirections.

FIGS. 5A to 5D show an example of tracks, recording/reproductiondirections, and address numbers. FIG. 5A shows a pattern of spiralgrooves in the first recording layer 104. FIG. 5B shows a pattern ofspiral grooves in the second recording layer 102. FIG. 5C shows therecording/reproduction directions of the optical disc 100. FIG. 5D showsassignment of address numbers. When the optical disc 100 is rotated, theoptical head 303 is moved from the inside circumference to the outsidecircumference on the first recording layer 104 along an inside track 502and from the outside circumference to the inside circumference on thesecond recording layer 102 along a track 501. When data is sequentiallyrecorded, for example, recording is performed from the most insidecircumference to the most outside circumference of the data area 114,and then from the most outside circumference to the most insidecircumference of the data area 110. Physical address numbers 503 andlogical address numbers 504 in each recording layer are incremented inthe recording/reproduction directions. Note that the second layer spiralhas a direction opposite to that of the first layer spiral. Therefore,the relationship between address number and radius is reversed. In thedata area 114 of the first layer, the logical address number 504 is 0 atthe most inside circumference and is incremented one by one toward theoutside circumference. In the data area 110 of the second layer, thelogical address number 504 is incremented one by one from the mostoutside circumference toward the inside circumference, starting from thegreatest number of the first layer plus 1. Reference numerals 505 and506 indicate lead-out areas (not shown in FIG. 1), which are provided inorder to allow the optical head 303 to follow a track even when theoptical head 303 overruns a data area.

In the case where as shown in FIGS. 5A to 5D, recording is performedfrom the most inside circumference to the most outside circumference ofthe data area 114, and then from the most outside circumference to themost inside circumference of the data area 110, particularly, if allrecording layer-specific parameter and format information is recordedtogether in a single disc information area, it is not necessary that theoptical head 303 goes back from the most outside circumference to thedisc information area at the most inside circumference.

Similarly, also in the case where only reproduction is performed, whenreproduction is performed from the most inside circumference to the mostoutside circumference of the data area 114, and then, from the mostoutside circumference to the most inside circumference of the data area110, particularly, if all recording layer-specific parameter and formatinformation is recorded together in a single disc information area, itis not necessary that the optical head 303 goes back from the mostoutside circumference to the disc information area at the most insidecircumference.

FIG. 6A shows a layout of recording layer-specific parameters andformats in the disc information areas 107 and 111. In FIG. 6A, #1indicates at least one of a parameter and a form at relating to a firstrecording layer 104, and #2 indicates at least one of a parameter and aformat relating to a second recording layer 102. FIG. 6A shows layoutsof disc information areas 601 to 603 and 609 in a two-layer disc. Thedisc information areas 601 to 603 and 609 correspond to the discinformation areas 107 and 111. An information layout of a discinformation area 604 is of a single-layer disc. Note that the layoutrule of the disc information area 601 to 603 and 609 in a two-layer disccan be applied to a multi-layer disc.

In the disc information areas 601 to 603 and 609, a plurality of sets ofrecording layer-specific parameter and format information are recorded.Thus, by recording a plurality sets, even if reproduction cannot beperformed on one area due to a scratch or dust, desired information canbe reproduced and obtained from another area.

The length of an area in which parameters and formats are recorded isdesirably the same irrespective of a layer to which the parameters andformats relate. In this case, the starting position of information canbe specified, thereby making it possible to reduce a waiting time ormaking it unnecessary to search for a starting position for eachrecording layer for each set. Therefore, the structure of arecording/reproduction apparatus can be simplified. For example, in adisc information area, the length of an area in which parameters andformats relating to the first recording layer 104 are stored is the sameas the length of an area in which parameters and formats relating to thesecond recording layer 102 are stored.

In the disc information area 601, a set of parameter and formatinformation for all recording layers is repeated 4 times. For example,data “0” is recorded in a remaining area 605 in the disc informationarea 601. In this case, when recording and reproduction are performedfrom the inside circumference to the outside circumference, by recordingparameters and formats for a recording layer to be first reproduced(e.g., the first recording layer 104 as a reference layer) at the mostinside circumference, it is possible to quickly obtain parameters andformats for a layer to be first reproduced, and it is possible toquickly correct irradiation power when the irradiation power isinappropriate for the layer to be first reproduced. An address assignedto an area storing parameters and formats relating to the firstrecording layer 104 in a disc information area is smaller than anaddress assigned to an area storing parameters and formats relating tothe second recording layer 102 in the disc information area. In thiscase, an address assigned to an area storing irradiation powerinformation relating to the first recording layer 104 in a discinformation area is smaller than an address assigned to an area storingirradiation power information relating to the second recording layer 102in the disc information area. With this feature, for example, it ispossible to minimize damage to data due to an excessively high level ofirradiation power.

Similarly, when reproduction is performed from the outside circumferenceto the inside circumference, by recording information for a recordinglayer to be first reproduced at the most outside circumference, it ispossible to quickly correct irradiation power when irradiation power isin appropriate for a layer to be first reproduced. Moreover, it ispossible to reproduce information from all recording layers quickly ascompared to 602 described below.

When the information amount of parameters and formats relating to thefirst recording layer 104 and the second recording layer 102 is small,the parameters and formats relating to the first recording layer 104 andthe parameters and formats relating to the second recording layer 102may be stored in an area having the same address assigned thereto in thedisc information area 107. It is now assumed that addresses are assignedin the first recording layer 104 along a circumference direction fromthe inside circumference to the outside circumference of the opticaldisc 100. In this case, an area in which the parameters and formatsrelating to the first recording layer 104 in the area having the sameaddress assigned thereto in the disc information area 107, is providedin a more inside circumference than an area in which the parameters andformats relating to the second recording layer 102 in the area havingthe same address assigned thereto in the disc information area 107.Alternatively, it is now assumed that addresses are assigned in thefirst recording layer 104 along a circumference direction from theoutside circumference to the inside circumference of the optical disc100. In this case, an area in which the parameters and formats relatingto the first recording layer 104 in the area having the same addressassigned thereto in the disc information area 107, is provided in a moreoutside circumference than an area in which the parameters and formatsrelating to the second recording layer 102 in the area having the sameaddress assigned thereto in the disc information area 107.

Note that in the disc information area 107 included in the secondrecording layer 102, an address assigned to an area in which theparameters and formats relating to the second recording layer 102 arestored may be smaller than an address assigned to an area in which theparameters and formats relating to the first recording layer 104 arestored. Therefore, even when reproduction is performed on the secondrecording layer 102 earlier than on the first recording layer 104, theparameters and formats relating to the second recording layer 102 can bequickly obtained. As a result, even when the irradiation power of laserlight irradiating the second recording layer 102 is inappropriate, theirradiation power can be quickly corrected.

Information indicating the amount of net data in the disc informationarea 601 excluding the area 605 (e.g., represented by in units of byte)may be recorded in the vicinity of the most inside circumference of thedisc information area 601. Therefore, a recording/reproduction apparatusdoes not reproduce unnecessary data and can perform a subsequent processquickly. The amount of net data may vary depending on a recording layer.Alternatively, the amount of net data may be recorded in the vicinity ofthe most inside circumference of a disc information area of eachrecording layer.

In the disc information area 601, a set of information for all recordinglayers is repeated 4 times. The present invention is not so limited.Information indicating the number of repetition may be recorded in thevicinity of the most inside circumference of the disc information area601. Thereby, a recording/reproduction apparatus does not reproduceunnecessary data and can perform a subsequent process quickly.

In the disc information area 602, a set of parameter and formatinformation for each recording layer is repeated 4 times. For example,data “0” is recorded in a remaining area 606 in the disc informationarea 601. In this case, by recording information for a recording layerto be first reproduced at the most inside circumference, it is possibleto quickly correct irradiation power when irradiation power isinappropriate for a layer to be first reproduced. In this case, anaddress assigned to an area storing parameters and formats relating tothe first recording layer 104 in a disc information area is smaller thanan address assigned to an area storing parameters and formats relatingto the second recording layer 102 in the disc information area. Sincethe layout of information in the disc information area 604 which is of asingle-layer disc is the same as the layout of information at the insidecircumference of the disc information area 602, it is possible toproduce the optical disc 100 whose reproduction algorithm has the sameform as that added to a single-layer optical disc. Therefore, it ispossible to simplify a recording/reproduction apparatus.

Information indicating the amount of net data in the disc informationarea 602 excluding the area 606 (e.g., represented by in units of byte)may be recorded in the vicinity of the most inside circumference of thedisc information area 602. Therefore, a recording/reproduction apparatusdoes not reproduce unnecessary data and can perform a subsequent processquickly. The amount of net data may vary depending on a recording layer.Alternatively, the amount of net data may be recorded in the vicinity ofthe most inside circumference of a disc information area of eachrecording layer.

In the disc information area 602, a set of information for eachrecording layer is repeated 4 times. The present invention is not solimited. Information indicating the number of repetition may be recordedin the vicinity of the most inside circumference of the disc informationarea 602. Thereby, a recording/reproduction apparatus does not reproduceunnecessary data and can perform a subsequent process quickly. Thenumber of repetition may vary depending on a recording layer. The numberof repetition of a set of information for each recording layer may berecorded in the vicinity of the most inside circumference of the discinformation area 602.

In the disc information area 603, parameter and format information forrecording and reproduction are divided into each element. Each specificelement is collected for all recording layers. Such a collection isrecorded as a set of information. Regarding a method for repetition, asin the disc information area 601, a set of information in which acomplete set of elements are arranged is repeated a plurality of times,or alternatively, as in the disc information area 602, an element isrecorded a plurality of times and then another element is recorded aplurality of times.

Data “0” is recorded in a remaining area 607 in the disc informationarea 603. By recording information for a recording layer to be firstreproduced at the most inside circumference, it is possible to quicklycorrect irradiation power when irradiation power is inappropriate for alayer to be first reproduced.

Information indicating the amount of net data in the disc informationarea 603 excluding the area 607 (e.g., represented by in units of byte)may be recorded in the vicinity of the most inside circumference of thedisc information area 603. Therefore, a recording/reproduction apparatusdoes not reproduce unnecessary data and can perform a subsequent processquickly.

By recording predetermined data in a remaining portion of the discinformation areas 601 to 604 in which parameter and format informationare recorded, when an optical head 203 is moved to a disc informationarea by a servo circuit 205, the disc information area can be quicklyrecognized by reproducing the predetermined data.

In the disc information area 601 to 603, information for each recordinglayer is recorded in a direction in which address numbers areincremented as shown in FIGS. 4D and 5D. For example, as shown in FIG.5D, when spiral directions are opposite to each other, physicalarrangement of information is reversed between the first recording layerand the second recording layer. For example, recording is performed onthe first recording layer from the most inside circumference portion ofa disc information area, while recording is performed on the secondrecording layer from the most outside circumference portion of a discinformation area. The present invention is not so limited.Alternatively, recording is performed on both the first and secondrecording layer from the most inside circumference portion of a disc.

In the disc information areas 601 to 603, parameter and formatinformation or disc information which are common to recording layers maybe recorded before recording information specific for each layer.Parameters and formats are recorded in accordance with such a method ina disc information area 609. By using a single set of common items, adisc information area can be relatively reduced as the number of layersis increased. By recording the common items a plurality of times similarto information #1 and #2 as in FIG. 6A, even if predeterminedinformation is not reproduced from an area due to a scratch or dust, theinformation can be reproduced and obtained from another area.

The length of an area for recording common items of recording layers isdesirably a multiple of the length of an area for recording informationof each recording layer. Therefore, even if the number of layers or theamount of common items is changed, it is easy for arecording/reproduction apparatus to predict the starting position ofinformation, thereby making it possible to reduce a waiting time and tosimplify the structure of a recording/reproduction apparatus.

Next, FIG. 6B shows a modified example of the disc information area 601,i.e., disc information areas 1101, 1102, 1103 and 1104. The discinformation areas 1101, 1102, 1103 and 1104 contain a plurality of dummyareas 1100.

In the disc information area 1101, a set of parameter and formatinformation for all recording layers is repeatedly recorded, and a dummyarea is provided between each area in which a set of information isrecorded. Therefore, by detecting the dummy area, it can be recognizedthat information #1 is recorded in an area immediately after the dummyarea or information #2 is recorded immediately before the dummy area.Therefore, it is no longer necessary to provide an identifier indicatinginformation #1 or #2 therein, whereby the structure of arecording/reproduction apparatus can be simplified and a processing timecan be reduced.

In the dummy area, the same contents as recorded in a remaining area1105 in a disc information area (e.g., data “0”) may be recorded, oralternatively, different contents may be recorded. By recordingdifferent contents, it can be clearly recognized that information #1 isrecorded in an area immediately after the dummy area or information #2is recorded immediately before the dummy area. Even if the same contentsare recorded, the dummy can be clearly distinguished from the area 1105by changing the recording length, resulting in the same effect.

By recording information common to information #1 and #2 in a dummy areaas show in the disc information area 609 (FIG. 6A), it can be recognizedthat information #1 is recorded in an area immediately after the dummyarea or information #2 is recorded immediately before the dummy area,and it is easy to obtain common information.

As shown in the disc information area 1102, a dummy area 1100 may becontiguous to an area 1106, whereby it can be recognized thatinformation #2 is recorded in at least an area immediately before thedummy data 1100. Note that only the last dummy area in the discinformation area 1102 may contain recording contents different fromthose of the other dummy areas. In this case, the end of the recordingrepetition can be clarified.

The length of a dummy area may be an integral multiple of the length ofan area in which a set of information #1 and information #2 arerecorded, as shown in a disc information area 1103. Therefore, even ifthe number of layers is different, it is easy to predict the startingposition of information in each recording layer, thereby making itpossible to reduce awaiting time and to simplify the structure of areproduction apparatus.

As shown in a disc information area 1104, a dummy area 1100 may berecorded before an area in which information #1 and information #2 arefirst recorded. Therefore, it can be recognized that information #1 isrecorded in at least an area immediately after the dummy data. Note thatonly the first dummy area in the disc information area 1104 may have thecontents different from the contents of the other dummy areas.Therefore, the start of repetition of recording can be clarified.

The setting of the first dummy area is not limited to theabove-described method, if a disc information area can be distinguishedfrom an area immediately before the disc information area. For example,an area immediately before a disc information area may be recognizedbased on the difference in a track shape or a modulation method foroverlaying information on the track shape.

Note that the dummy data shown in FIG. 6B can be used in the discinformation area 602, resulting in substantially the same effect as whenapplied to the disc information area 601.

As described above, by recording recording layer-specific parameter andformat information required for performing recording and reproduction oneach recording layer in a single disc information area, a time requiredto record and reproduce data from a plurality of layers can be reducedas compared to when information is reproduced from a plurality of discinformation areas provided in a plurality of layers.

In this embodiment, the disc information area is mainly described. Inaddition, regarding a defect list area and a spare area, the same effectis obtained by recording information for each recording layer in asingle layer.

In this embodiment, recording layer-specific parameter and formatinformation required for performing recording and reproduction on eachrecording layer is recorded in a single disc information area.Alternatively, all of such information may not be recorded in a singledisc information area and may be divided and recorded in a plurality ofdisc information areas. Alternatively, a predetermined essentialinformation item(s) for each recording layer may be recorded in a singledisc information area, while other items may be recorded in a discinformation area of each layer.

Note that parameters and formats recorded in a disc information area maybe recorded in tracks in the defect list area 108, the spare area 109,the data area 110, the defect list area 112, the spare area 113, dataarea 114 in accordance with the layouts shown in FIGS. 6A and 6B.

Next, a rewritable optical disc 900 according to another embodiment ofthe present invention will be described with reference to FIG. 9.

The optical disc 900 of FIG. 9 comprises a first substrate 905, a firstrecording layer 904, an adhesive resin 903, a second recording layer902, and a second substrate 901. Each substrate and each recording layerare provided with a clamp hole 906. The optical disc 900 comprises adata area 920 for recording user data. The data area 920 is provided inboth the first recording layer 904 and the second recording layer 902. Adata area 912 which is a portion of the data area 920 is provided in thesecond recording layer 902, while a data area 918 which is the otherportion of the data area 920 is provided in the first recording layer904.

The second recording layer 902 comprises a disc information area 907, afirst defect list area 908, a test recording area 909, a second defectlist area 910, a spare area 911, and a data area 912.

The first recording layer 904 comprises a disc information area 913, afirst defect list area 914, a test recording area 915, a second defectlist area 916, a spare area 917, and a data area 918.

The first recording layer 904 and the second recording layer 902 areprovided on a single side of the optical disc 900.

It is desirable that the same data is recorded in the first defect listarea and the second defect list area in each recording layer. The samedata may be recorded in a defect list area in all recording layers.Thereby, when the spot of laser light is moved between recording layersin recording or reproduction, a time required for reproduction of adefect list area in a destination layer can be saved.

The test recording area 909 functions as an adjustment area forperforming test recording for adjusting the recording power of laserlight for recording information in the data area 912. Similarly, thetest recording area 915 functions as an adjustment area for performingtest recording for adjusting the recording power of laser light forrecording information in the data area 918. As in this embodiment, byproviding a test recording area in each recording layer, it is possibleto determine recording conditions suitable for each recording layer.

When the spot of laser light is vertically shifted from one layer toanother layer, it is difficult to locate the spot at the same radialposition due to misalignment of substrates attached together,misalignment of the clamp holes of the substrates, or the like. Forexample, when it is attempted to move from the 1000^(th) track from theinside circumference of the first recording layer 904 to the 1000^(th)track from the inside circumference of the second recording layer 902,an error of about ±50 tracks occurs.

In a test recording area, recording conditions are determined byperforming test recording under unstable servo recording conditions. Inthis case, there is the risk of tracking being displaced duringrecording or the risk of laser light coming into focus instantaneouslyon an unintended layer. To avoid these risks, a buffer area in which nointended use is defined is desirably provided contiguously before andafter the test recording area of each recording layer. It is alsopreferable that a plurality of defect list areas are provided before andafter the test recording area as shown in FIG. 9. By providing defectlist areas before and after the test recording area of each recordinglayer, the risk of damaging all data in a defect list area can bereduced even if tracking is displaced during recording data. Further,when focus is displaced during recording of information to a certainrecording layer, the risk of damaging all data in a defect list area ofanother recording layer can be reduced.

In this embodiment, a defect list area is provided only in the insidecircumference portion of each recording layer. From the same viewpoint,a defect list area may be provided in the outside circumference portion.By providing the outside circumference portion, it is possible toprevent damage to data in a defect list area due to test recording.

Note that parameter and format information specific for each recordinglayer may be recorded together in a single disc information area.Alternatively, each recording layer may separately contain parameter andformat information.

A test recording area in each recording layer may be located at adifferent radial position as shown in FIG. 10. FIG. 10 shows an opticaldisc 1000, which is a modification of the optical disc 900, comprising afirst substrate 1005, a first recording layer 1004, an adhesive layer1003, a second recording layer 1002, and a second substrate 1001.

The second substrate 1001, the second recording layer 1002, the adhesivelayer 1003, the first recording layer 1004, and the first substrate 1005correspond to the second substrate 901, the second recording layer 902,the adhesive layer 903, the first recording layer 904, and the firstsubstrate 905, respectively. The second recording layer 1002 and thefirst recording layer 1004 have the same components as those of thesecond recording layer 902 and the first recording layer 904,respectively, except that the location of a test recording area isdifferent. The second recording layer 1002 comprises a test recordingarea 1008. The first recording layer 1004 comprises a test recordingarea 1007.

Reference numeral 1009 indicates incident light. Reference numeral 1010indicates light reflected from the second recording layer 1002.Reference numeral 1011 indicates light transmitted through the secondrecording layer 1002. Reference numeral 1012 indicates light reflectedfrom the first recording layer 1004. Reference numeral 1013 indicateslight transmitted through the second recording layer 1002. Thesereference numerals indicate paths of laser light. When reproduction isperformed on the second recording layer 1002, the reflected light 1010is a main reproduction light while the transmitted light 1013 isunnecessary stray light. When reproduction is performed on the firstrecording layer 1004, the transmitted light 1013 is a main reproductionlight while the reflected light 1010 is unnecessary stray light.

It is now assumed that a test recording area for determining theirradiation power of laser light for recording data in the recordinglayer 1004 is provided at the position of the area 1006. In this case,if the test recording area 1008 is degraded or damaged (e.g., due torepetition of recording), the transmittance coefficient or reflectancecoefficient of the second recording layer 1002 is changed, resulting inchanges in the transmitted light 1011, the reflected light 1010 and thetransmitted light 1013. Therefore, as is different from when the testrecording area 1008 is normal, the value of the irradiation powerobtained using the test recording area 1006 departs from the correctirradiation power.

As shown in FIG. 10, by providing the test recording area 1007 and thetest recording area 1008 at different radial positions of the opticaldisc 1000, it is possible to correctly determine the value of theirradiation power of laser light suitable for the first recording layer1004 even when the test recording area 1008 is degraded or damaged.

As described above, arrangement of the test recording areas of eachrecording layer at a different radial position is very effective whenthe optical disc 1000 is a write-once-read-many optical disc capable ofrecording only once, particularly an optical disc having a irreversiblerecording film whose optical characteristics are changed by recording.The present invention is applied to such an optical disc capable ofrecording only once.

In this embodiment, a test recording area in each recording layer isprovided at a different radial position. Alternatively, in addition tothe test recording area, for example, an area for managing a list of alldata recorded in an optical disc or the like, which is repeatedlyrecorded a predetermined number of times which is greater than thenumber of repetitions of recording in an area in which normal user datais recorded, may be positioned at a different radial position in eachrecording layer. By providing such areas at different positions, it ispossible to prevent degradation of the area in one layer from affectingthe area in another layer, whereby recording and reproduction can beperformed on the area in the other layer.

In this embodiment, the test recording area 1007 is provided at theoutside circumference side with respect to the radial direction.Alternatively, the test recording area 1008 may be provided at theoutside circumference side with respect to the radial direction. Forexample, in the case of the recording/reproduction directions as shownin FIG. 5C, the test recording area 1007 may be used from the insidecircumference side, while the test recording area 1008 may be used fromthe outside circumference side. In this case, when the test recordingarea 1008 is used, the probability that the most outside circumferenceside of the test recording area 1007 is not used is higher than when itis used. Therefore, an influence of degradation of the test recordingarea 1007 on the test recording 1008 can be further reduced. The effectis very large for an optical disc capable of recording only once.

In this embodiment, a test recording area is provided only on the insidecircumference side. Alternatively, it may be provided on the outsidecircumference side.

The present invention is not limited to an optical disc having arecordable recording layer. If an optical disc having a plurality ofreproduction-only recording layers has a disc information area, the sameeffect is obtained according to the present invention.

In this embodiment, recording is performed on two layers, i.e., thefirst recording layer and the second recording layer. When the presentinvention can be applied to a single-layer disc, the same effect can beobtained.

In this embodiment, a rewritable optical disc is mainly described. Thepresent invention can be applied to a recordable optical disc in whichrecording can be performed once or several times and the same effect canbe obtained.

According to the optical disc of the present invention, parameters andformats specific for each recording layer required for performingrecording and reproduction on the recording layer is recorded togetherin a single disc information area. With this feature, parameters andformats for each recording layer can be reproduced from a single discinformation area, thereby making it possible to reduce a time requiredfor recording and reproduction of data for a plurality of recordinglayers.

Various other modifications will be apparent to and can be readily madeby those skilled in the art without departing from the scope and spiritof this invention. Accordingly, it is not intended that the scope of theclaims appended hereto be limited to the description as set forthherein, but rather that the claims be broadly construed.

1. An information recording medium comprising: a plurality of recordinglayers; a test area for determining a recording power of a laser lightfor each of the plurality of recording layers, and a plurality of bufferareas, wherein a first test area of a first layer and a second test areaof a second layer adjacent to the first layer are provided at differentradial positions such that the first test area of the first layeroverlaps a region of the adjacent second layer provided for purposesother than a test area, the first test area being located closer to aninside circumference side and the second test area being located closerto an outside circumference side, wherein a first buffer area among theplurality of buffer areas is located just before the first test area, asecond buffer area among the plurality of buffer areas is located justafter the first test area, a third buffer area among the plurality ofbuffer areas is located just before the second test area, a fourthbuffer area among the plurality of buffer areas is located just afterthe second test area, wherein a recording power of the first layer isdecided by using the first test area from the inside circumference side,and wherein a recording power of the second layer is decided by usingthe second test area from the outside circumference side.
 2. Areproducing method for information from an information recording mediumaccording to claim 1, the method comprising: reproducing a data recordedwith the determined recording power.
 3. A method for determining arecording power for an information recording medium, the mediumincluding: a plurality of recording layers; a test area for determininga recording power of a laser light for each of the plurality ofrecording layers; and a plurality of buffer areas, wherein a first testarea of a first layer and a second test area of a second layer adjacentto the first layer are provided at different radial positions such thatthe first test area of the first layer overlaps a region of the adjacentsecond layer provided for purposes other than a test area, the firsttest area being located closer to an inside circumference side and thesecond test area being located closer to an outside circumference side,wherein a first buffer area among the plurality of buffer areas islocated just before the first test area, a second buffer area among theplurality of buffer areas is located just after the first test area, athird buffer area among the plurality of buffer areas is located justbefore the second test area, a fourth buffer area among the plurality ofbuffer areas is located just after the second test area, the methodcomprising: determining a recording power of the first layer by usingthe first test area from the inside circumference side, and determininga recording power of the second layer by using the second test area fromthe outside circumference side.